Various electronic apparatuses such as mobile phones and personal digital assistants (PDAs) have been widely used, and it has been demanded to further reduce size and weight of the electronic apparatuses and to achieve their longer lives. Accordingly, batteries, in particular, small and light-weight secondary batteries that have ability to achieve high energy density have been developed as power sources for the electronic apparatuses.
Applications of the secondary batteries are not limited to the electronic apparatuses described above, and it has been also considered to apply the secondary batteries to various other applications. Examples of such other applications may include: a battery pack attachably and detachably mounted on, for example, an electronic apparatus; an electric vehicle such as an electric automobile; an electric power storage system such as a home electric power server; and an electric power tool such as an electric drill.
There have been proposed secondary batteries that utilize various charge and discharge principles in order to obtain battery capacity. In particular, attention has been paid to a secondary battery that utilizes insertion and extraction of an electrode reactant and a secondary battery that utilizes precipitation and dissolution of an electrode reactant, which make it possible to achieve higher energy density than other batteries such as a lead-acid battery and a nickel-cadmium battery.
The secondary battery includes a cathode, an anode, and an electrolytic solution. The configuration of the secondary battery exerts a large influence on battery characteristics. Accordingly, various studies have been conducted on the configuration of the secondary battery.
More specifically, in order to improve, for example, ionic conductivity of a polymer solid electrolyte, a vinylidene fluoride-based copolymer is used as a polymer matrix (for example, refer to PTL 1). In order to improve heat resistance of a separator, an electrolyte layer contains insulating particles (for example, refer to PTL 2). In order to improve a pot life of a polymer solid electrolyte, a reactant such as an amino resin is used as a cross-linked resin (for example, refer to PTL 3).